In the stream of commerce, it is desirable to keep track of products shipped from a manufacturer or seller to a customer or end user in order to protect the product from loss or theft. Incidences of lost or misplaced cargo can detract significantly from the bottom line for both shipping companies and uninsured purchasers of lost or stolen products. Keeping track of where a particular package is located while enroute to a customer is a labor intensive task for the shipping company handling the package. In addition, the customer must rely on the shipping company to provide the current whereabouts of the product while enroute, and/or must access the shipping company's web site in order to locate that information.
Any shipping information known by the manufacturer or seller of a product is usually restricted to the information supplied at the time a shipping company takes physical possession of the product and identifies it by using, for example, an optical scanner.
While radio frequency identification (RFID) has been implemented in an effort to automate the tracking process (i.e., eliminate the reliance on a human package handler to provide the tracking information), the basic problem still remains: information cannot be easily obtained concerning the whereabouts of a package while en route. To resolve this problem, a low cost, compact, and unobtrusive means is needed to provide accurate tracking information of a package.
One method involves the use of bar codes and scanners. However, this method requires close proximity between the product carrying the bar code and the scanner.
Another method relies on RFID systems, which use radio frequency (RF) transponders to transfer information to interrogation stations. Unlike other information communication systems, RF transponder systems are not restricted to line-of-sight or hard-wire communications, and are most desirable where wireless communications are a necessity. Information transferred by a RF transponder system typically comprises identification data, but can also include messages, depending on the sophistication of the electronics used in the system.
RFID systems include an interrogator, which typically employs an exciter that transmits a RF excitation signal, and a transponder. The transponder is energized by the excitation signal to transmit a signal, including an identification code or other information, back to the interrogator. This is accomplished when the transponder receives a RF signal, or, more specifically, is energized by the RF magnetic field, and then forms a response signal that will identify the transponder and/or may provide additional information. The transponder then transmits the response signal to the interrogator. The interrogator includes a receiver that receives the response signal and processes the information it contains. This information is then recorded by a data management system.
One method of RFID works on an inductive principle where an interrogation station generates a magnetic field at a predetermined frequency. When the transponder enters this magnetic field, a small electric current is formed in the transponder, which provides power to the RFID electronic control components. These components then modulate the magnetic field in order to transmit the transponder's programmed data back to the interrogator. The interrogator receives the signal transmission, demodulates and decodes the transmission, and sends the data on to a host computer for further processing.
RF transponders are classified as either passive or active. Passive RF transponders extract their power from the electromagnetic field provided by the interrogator. An active RF transponder includes a radio transceiver and a battery power source, which enables it to transmit a signal to a remote receiver. The advantage of using active transponders is that they typically have increased range over passive transponders, but the disadvantage is that they require a battery power source to achieve that increased range.
Desirable though these RFID systems are, there have been problems with size, cost, and reliability.
Solutions to these problems have been long sought, but have also long eluded those skilled in the art.